混凝土变电压RCM试验的边部效应研究

Research on the edge effect for variable voltage RCM test of concrete

通过氯离子快速迁移(RCM)试验测试混凝土中氯离子扩散系数时由于存在边部效应,导致混凝土试件与橡胶套相邻部位的氯离子扩散深度明显大于试件中心部分的扩散深度。为此通过对混凝土RCM试验结果的统计分析,系统研究了边部效应及其对氯离子扩散系数测试结果的影响,建立了修正计算式。首先进行74组混凝土试件的变电压RCM试验,并定义试件上各个测点氯离子扩散深度的标准值;然后通过对试验实测结果的统计分析得到试件各个测点上氯离子标准扩散深度的均值及标准差,并据此定量分析边部效应的范围及其对氯离子扩散深度及扩散系数的影响;最后,通过回归分析建立排除边部效应试验结果与传统的不排除或部分排除边部效应试验结果之间的转换关系。研究表明,边部效应对直径100 mm圆柱形混凝土试件的影响范围为试件外边缘至试件内部20 mm深的区域,排除边部效应的影响能够有效减少结果波动性,从而提高RCM试验的准确性。

The edge effect,resulting from possible leakage in RCM test,and causing the chloride diffusion depth in the edge part of concrete specimen greater than that in the central part,was investigated systematically to analyze its influence on the chloride diffusion coefficient of concrete based on statistical analysis of the RCM test data of the concrete specimen,while the revised calculation expression of the diffusion coefficient was developed in this study.Firstly,variable voltage RCM tests were performed on 74 sets of concrete specimens.Secondly,the normalized depth was defined for chloride diffusion at observation points along the axial section of the specimen.Then the influence of edge effect on the diffusion depth and diffusion coefficient of chloride ion was quantitatively analyzed based on the results of variable voltage RCM test.Finally,the correlation between the diffusion coefficient for the center part of axial section of the specimen and that for the whole section were quantitatively investigated,thus providing a basis to calibrate the chloride diffusion coefficient obtained by existing experimental technique.Results show that the influence range of edge effect on 100 mm diameter cylindrical concrete specimen is from the outer edge of specimen to the depth of 20 mm inside specimen,while the deviation of chloride diffusion coefficient of concrete increases due to the edge effect in the variable voltage RCM test,hence the accuracy of the tested chloride diffusion coefficient can be improved by obviation of the edge effect on the chloride diffusion depth in concrete specimen.